The terahertz (THz) wave is an electromagnetic wave having a frequency range of approximately 0.1 to 10 THz (1 THz=1012 Hz). It represents a special region in electromagnetic spectrum where it overlaps the millimeter wave in its long-wave direction and overlaps the infrared in its short-wave direction. However, due to technical limitations, the research into THz wave lag far behind those into the millimeter wave and infrared ray, which makes it the last frequency window to be fully explored in the electromagnetic spectrum. It is called the “THz gap”. However, the THz wave has a series of unique properties, making it not only academically important in basic science, but also applicable in science and technology as well as in industry. The THz wave is in the transition zone from the macroscopic classical theory to the microscopic quantum theory, and is also in the transition zone from electronics to photonics, covering in frequency domain the rotation and oscillation frequency of a variety of macromolecules, including proteins. Also, it has a very low quantum energy which will not damage materials, and thus has a great advantage over X-ray and will become a very powerful tool in studying various substances, especially living substance. The wavelength of THz wave is over 1000 times shorter than that of microwave, which gives it such a high spatial resolution that it can be used in information science for high spatial and temporal resolution imaging, signal processing, large-capacity data transmission and broadband communication. In addition, the THz wave also has broad application prospects in materials evaluation, layered imaging, biological imaging, plasma fusion diagnosis, astronomy and environmental science, and even in drug testing, weapon search and military intelligence collection.
Both the detector and the radiation source of the THz wave play a foundational and key role in the THz technology, which have already become the domestic and foreign research hotspot. The device based on planar nanostructures has attracted more and more attention with its simple manufacturing, easy integrating and low parasitic capacitance. In March 2008, CN02808508.6 (Publication No. CN100377354C) disclosed a planar diode device of nanometric dimensions. The device is obtained by etching insulated lines in a conductive substrate to define charge carrier flow paths by using nano-etching technique. The device can be used to construct a full family of logic gates, such as OR, AND and NOT, and construct a rectifier for detecting electromagnetic waves. Recent experiments show that such devices can detect electromagnetic waves with a frequency up to 1.5 THz at room temperature, and that the detection frequency can be increased to 2.5 THz if the operating temperature is lowered to 150K. Since such a device has a negative differential resistance under reverse bias voltage, it can be used as a key component of an oscillation circuit. Then, CN200810219701.9 (Publication No. CN101431106A) disclosed a spontaneously-oscillating planar nano-electromagnetic radiation device, and the key method for manufacturing the same.
As oscillators with nonlinear periodic systems get close to one another, their oscillating phases will change due to the coupling effect and further abundant phenomena such as in-phase (synchronous) oscillation, phase-locked oscillation and inverse oscillation will occur. Related research in the field of science and technology has always been attached great importance. The earliest research can be traced back to February 1665 when the famous physicist Huygens made an observation of two pendulums. Later it was found that the phase-locked phenomena abound in nature and daily life, as illustrated by the fact that the congregated fireflies will spark simultaneously, that cardiac pacing cells beat consistently, and that mother and baby have the same heart rate. The Adler equation is the milestone in the field of electronics. It tells people how weak coupling LC oscillators will work when they are arranged in arrays. For the nano-oscillator, using phase-locked technology to produce phased array can not only improve the output power of the device, but also develop a directional radiation source for wireless communication.
Although phase issues are critical to an oscillator array, CN200810219701.9 (Publication No. CN101431106A) does not disclose key techniques related to phase locking, nor does it disclose an oscillator array having phase locking function. Moreover, the follow-up studies have been devoted to studying how to improve the performance of a single planar nano-oscillator (A. Íñiguez-de-la-Torre, I. Íñiguez-de-la-Torre, J. Mateos, T. González, P. Sangaré, M. Faucher, B. Grimbert, V. Brandli, G. Ducournau and C. Gaquière, “Searching for THz Gunn oscillations in GaN planar nanodiodes”, J. Appl. Phys. 111, 113705 (2012); J.-F. Millithaler, I. Iñiguez-de-la-Torre, A. Iñiguez-de-la-Torre, T. González, P. Sangaré, G. Ducournau, C. Gaquière, and J. Mateos, “Optimized V-shape design of GaN nanodiodes for the generation of Gunn oscillations”, Appl. Phys. Lett. 104, 073509 (2014)).